Manual compound transmissions are used for various vehicle applications. Such compound transmissions typically comprise a multiple speed main section containing a plurality of gears for various range and load gearing configurations.
Manual compound transmissions are generally positioned within a driveline adjacent a primary drive unit with at least one rotating drive shaft. These compound transmissions generally include a shifter or gear selector that extends from the transmission for interaction with an operator. The compound transmission may include a rotating and sliding assembly that is configured to engage a desired gear set when an operator moves the shifter or gear selector. Specifically, in a manual compound transmission an operator, through the gear selector, selects an appropriate gear by pushing or pulling the shift lever to a desired shift gate. A rail selector fixed to the main shift rail is configured to translate the movement of the shift lever to the shift forks. The rail selector is fixed to the main shift rail by a roll pin that extends through a central location of the rail selector. The action on the shift lever causes a set of shift rails to move at least one shift fork, which causes a shift collar to slide over the appropriate rotating gear to synchronize and activate a desired gear range.
Shift quality is an important factor for manual compound transmissions when selecting the desired gear range. There are many factors affecting shift quality, such as, but not limited to shift force, notchness from bumps and detents, nibble, and precision of the rotating and sliding components, such as, but not limited to end stop feel and lash. Nibble may be defined as a form of partial clash following a successful synchronizing action. It may result from a speed differential generated during the period between indexing and final engagement of the teeth for the desired gear. Unfortunately, the previously discussed factors affecting shift quality are typically transmitted directly through the rotating components and shift rails, as the previous designs included shift components that were fixed directly to the shift rail. These factors are transmitted directly through the components, through the shift lever and ultimately to the operator.
The shift quality is important to provide the operator with the appropriate feedback through the shift lever indicating that the compound transmission is engaged in the appropriate gear set while preventing a mis-shift or other misalignment that may potentially damage or shorten the life of the transmission. The shift quality is also important for preventing fatigue and possible injury to the operator as the feedback carried through the shift lever may result in damage to the operators hand, wrist, arm or shoulder.
Therefore, it is desirable to provide a manual compound transmission system that allows for improved synchronization of the meshing components, while providing an additional damping mechanism to improve shift quality and an operator's shifting experience, thereby providing a smooth end stop feel preventing operator fatigue and providing prolonged transmission life.